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PRINCIPLES OF CROP GROWTH SIMULATION MODELLING
Water-limited production
The Rice System and boundaries –Water-limited production situation
Radiation, CO2, H2O O2 , H2O
H2O H2O
H2OH2O Root zone
Temperature,Wind speedVapor pressure
Root water uptake
Crop transpiration
Affectscropgrowth
I. Growth as affected by water availability in soil
Soil water tension (“drought”) affects: transpiration,
photosynthesis, leaf rolling, spikelet sterility, leaf
expansion, assimilate partitioning, rooting depth, leaf
death
II. Water availability as function of soil water balance
Soil water tension = f(soil water content) Soil water content = f (rain, irrigation, evaporation, transpiration, percolation, seepage, overbund flow)
PROCESSES OF CROP GROWTH
I. Growth as affected by water availability in soil
Leaf
Stem
Root
Drought-stress effects derived from pot experiments, IRRI (Wopereis et al., 1996)
New research in progressNieuwenhuis et al., 2002
1. Transpiration and photosynthesis
Principle of reduction in photosynthesis by single leaf caused by water-stress
• Rate of CO2 flow through leaf stomata is equal to rate of H2O flow
• Stomatal aperture determines both CO2 and H2O flow rates
• When water supply (soil) is limiting, stomata close => CO2 and H2O flow rates decrease proportionally:
Fact = (Tact/Tpot) Fpot
Rice variety IR72
leaf (Tact/Tpot)
Soil water tension
• Actual photosynthesis (Fact) = relative transpiration x potential photosynthesis (Fpot)
Potential production routines
• Actual transpiration (Tact) = relative transpiration x potential transpiration (Tpot)
• Penman-Monteith
• Makkink
• Priestley-Taylor
Penman Priestley-Taylor
Makkink
Geographic latitude X X
Surface reflection coefficient
X X
Angstrom coefficients
X
Radiation/sunshine X X X
Temperature X X X
Wind speed X
Vapor pressure X
Required input data for calculation of Tpot
1
2
3
4
5
6
7
0 10 20 30 40 50 60 70 80 90 100 110 120
TIME
0
1
2
3
4
5
6
7
0 10 20 30 40 50 60 70 80 90 100 110 120
TIME
Potential transpiration (mm d-1)
Reference ET (mm d-1)
Penman
Makkink
ET and T,
Dry season 1992,
Los Baños
2. Leaf rolling
0
0.2
0.4
0.6
0.8
1
1.2
1 10 100 1000 10000
Leaf rolling factor (-)
Soil water tension (kPa)
Rolled leaves => less canopy photosynthesis;
less canopy transpiration
3. Spikelet sterility
Turner (1986): relationship between leaf
rolling – increased canopy temperature
T = 5 (1 – LRF) 1.6
LRF = leaf rolling factor
Spikelet sterility
4. Leaf expansion, partitioning and root depth
Wopereis et al. (1996): leaf expansion stops at
soil moisture potentials of 50 to 250 kPa:
reduced-leaf-expansion factor
Tuong et al.: expansion stops between 1.45 and
1404 kPa.
Less leaf area => less canopy photosynthesis Assimilates don’t go to leaves but are
redirected to roots => changed assimilate
partitioning and increased rooting depth
5. Accelerated leaf death
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1 10 100 1000 10000
Drought-induced leaf death factor factor (-)
Soil water tension (kPa)
Less leaves => less canopy photosynthesis;
less canopy transpiration
0
0.2
0.4
0.6
0.8
1
1.2
1 10 100 1000 10000
Reduction factor (-)
Soil water tension (kPa)
Leaf expansion,Partitioning,Root depth
Leaf death
Leaf rolling,Spikelet sterility
Leaf photosynthesis,transpiration
Summary effects of soil water tension; IR72
Summary effects of soil water tension
Less leaves
Reduced leaf expansion
Less canopy photosynthesis
Less biomass
Reduced partitioning to shoot
Reduced leaf photosynthesis, transpiration
Leaf rollingLess light interception
Spikelet sterility
Less grainsLess yield
Accelerated leaf death
Soil moisture tension
Less canopy transpiration
II. Soil water balance
Schematic representation of the factors involved in a water balance, indicating water storage and flow in the plant-soil-atmosphere system. E - evaporation;T - transpiration; P - precipitation;I - irrigation; R - run-on/off; D - drainage; C - capillary rise; S - moisture content in the root zone.
Water balanceupland soil
Upland and aerobic rice
Lowland rice
Water balance lowland rice soil
Water requirements in lowland rice
Daily
(mm d-1)
Season 100 d (mm)
Land preparation 175 - 750
Evapotranspiration- wet season- dry season
4 – 5
6 - 7
400 – 500
600 - 700
Seepage & percolation- heavy clay- sandy/loamy soil
1 – 5
25 – 30
100 – 500
2500 - 3000
Total season : 675-4450 mm Typical value : 1500-2000 mm
Water (mm) SP (mm d1)
Guimba 88
89
90
91
2197
1679
2028
3504
18.3
12.5
16.4
32.8
Muñoz 91 1019-1238 5.2-7.6
Talavera 93 577- 728 0.3-2.0
San Jose 97 2874 25.8
San Jose 96
97
1417 (DS)
1920 (DS)
9.6
15.2
PhilRice 01 600 1.1 (-> 4.4)
Water use; central Luzon
Puddled soils for lowland rice
Transpiration
Evaporation
Rainfall
Irrigation
Tension (1), content (1)
Tension (n), content (n)
Water in1, water out1
Water inn, water outn
n soil layers
N puddled layers
Soil water balance inputs
Rainfall Weather station
Irrigation Irrigation subroutine
Potential soil evaporation PenmanMakkinkPriestley-Taylor
Actual crop transpiration PenmanMakkinkPriestley-Taylor +Crop subroutine
Irrigation scheduling subroutine
• Irrigation is 0: purely rainfed• Irrigation is input data• Irrigation timing as function of threshold values in depth of ponded water on soil surface• Irrigation timing as function of threshold values in soil water content• Irrigation timing as function of threshold values in soil water tension• Irrigation applied at X days after disappearance of ponded water on soil surface
Three soil water balance models:• SAWAH: puddled or upland soils • PADDY: puddled soils• SAHEL: free-draining upland soils
Simulated output:• Soil water content in each soil layer• Soil water tension in each soil layer• Actual soil evaporation• Water flows between each soil layer
Soil water balance inputs -
soil properties:
• Number and thickness of soil layers (n)• Bund height• Maximum rooting depth (obstructive layer)• Groundwater depth• Initial states (water content per layer)
• Soil hydrological characteristics: - soil water retention curve - soil water conductivity curve
0
1
2
3
4
5
6
7
0 0.1 0.2 0.3 0.4 0.5 0.6
-12
-10
-8
-6
-4
-2
0
2
4
0 0.1 0.2 0.3 0.4 0.5 0.6
Soil water tension (pF= log(h))
Soil water conductivity (log(cm d-1))
Soil water content (cm 3 cm-3)
Clay
Sand
Soil hydrological
characteristics:
Water retention curve
(pF curve)
Conductivity curve
SAWAH PADDY SAHEL
Conductivity curve
Simple Rijtema X
Extended Rijtema X
van Genuchten X X
Power function X X
Retention curve
Driessen X
van Genuchten X X
Simple data (4) X X
Extended data (10) X
Options for soil hydrological characteristics
)2)(/11(
21/11
)1(
))1(()(
lnn
nnn
s h
hhKhK
nrs
rh
h/11)1(
)(
Van Genuchten equations
Retention curve
Conductivity curve
Ks = Saturated conductivity
s = Saturated water content
r = Air-dry water content
= parameter
n = parameter
l = parameter
Sand Clay
Air dry
(pF = 7)
0.001 0.22
Wilting point
(pF = 4.2)
0.03 0.34
Field capacity
(pF = 2)
0.30 0.48
Saturation
(pF = 0)
0.46 0.560
1
2
3
4
5
6
7
0 0.1 0.2 0.3 0.4 0.5 0.6
Soil water tension (pF= log(h))
Soil water content (cm 3 cm-3)
Clay
Sand
Simple data (4) retention curve
Crop model Water-limited Production
Photosynthesis
Assimilatepool Biomass
Leaves
Stems
Panicles
Roots
LAI
Developmentstage
Maintenancerespiration
Growthrespiration
Partitioning
Developmentrate
N leaves
Light
Transpiration
Soil water Soil-watertension
Evaporation Rain, irrigation
Temperature
Input
1. Weather data: daily temperature, radiation, (wind speed, humidity), rainfall => Weather file
2. Management, additional: irrigation application => Experiment data file
3. Crop characteristics, additional: drought response factors => Crop data file
4. Soil properties: layers, retention characteristics, conductivity characteristics => Soil data file
Experimental data file*---------------------------------------------------------------** 6. Irrigation parameters * Need only to be filled-in when PRODENV = 'WATER BALANCE'*---------------------------------------------------------------*** Select from the following options:*SWITIR = 0 ! No irrigation; rainfed*SWITIR = 1 ! Irrigation supplied as input dataSWITIR = 2 ! Irrigation at minimum standing soil water depth*SWITIR = 3 ! Irrigation at minimum soil water potential*SWITIR = 4 ! Irrigation at minimum soil water content*SWITIR = 5 ! Irrigation at X days after disappearance of standing water
** If SWITIR = 1, supply irrigation table, amount of irrigation ** (y in mm) for a given calendar * day (x), used if RIRRIT = 0., 20.,366., 20.
** If SWITIR = 2-5, supply amount of irrigation IRRI (mm) IRRI = 75. ! Irrigation gift (mm)
** If SWITIR = 2, supply minimum standing water depth WL0MIN (mm)** below which irrigation water is appliedWL0MIN = 10. ! Minimum standing water depth (mm)
** If SWITIR = 3-4, supply minimum soil water potential KPAMIN (KPa)** (for SWITIR=3) or minimum soil water content WCMIN (-) (SWITIR=4)** below which irrigation water is applied, and the soil layer to** which this potential applies SLMIN (-)KPAMIN = 50. ! Minimum soil water potential (Kpa)WCMIN = 0.30 ! Minimum soil water content (-)SLMIN = 4 ! Soil layer for which KPAMIN or WCMIN applies (-)
** If SWITIR = 5, supply number of days after disappearance of** standing water (WL0DAY) at which irrigation water is appliedWL0DAY = 3 ! number of days after disappearance of (-) INTEGER!!
Output
• Time course of leaf area index, biomass
of various crop organs
• Time course of soil water content and
soil water tension; evapotranspiration
• Yield, yield components
• Irrigation scheduling
Jakenan, Indonesia, IR64: biomass
Calendar day
40 60 80 100 120 140 160 180 200
Dry matter, kg ha-1
0
3000
6000
9000
12000
15000
18000WiTnS1, measuredWrTnS1, measuredWiTnS2, measuredWiTdS1, measuredWrTdS1, measuredWrTdS2, measuredWiTnS1, simulatedWrTnS1, simulatedWrTnS2, simulated
Irrigated
Rainfed early
Rainfed late
1996
(a) April-June 1995 (walik jerami season)
A M J J A
Water table depth, cm
-140
-120
-100
-80
-60
-40
-20
0
(b) December 1997-March 1998 (gogorancah season)
D J F M A
-140
-120
-100
-80
-60
-40
-20
0
20
measuredsimulated
(c) November 1998-February 1999 (gogorancah season)
Day of seeding
N D J F M
-120
-100
-80
-60
-40
-20
0
20
40
Jakenan, Indonesia: groundwater depth
0
20
40
60
80
100
90 100 110 120 130 140 150
Rainfed early; 20 cm depth
Day
kPa
0
20
40
60
80
100
120 130 140 150 160 170
Jakenan, 1996. WrTdS2, 20 cm
Day
Kpa Rainfed late; 20 cm depthkPa
Jakenan, Indonesia: soil water tension
Hyderabad, India
Irrigated and rainfedyield
0
2000
4000
6000
8000
10000
12000
14000
16000
0 50 100 150 200 250 300 350 400
Paddy yield (kg/ha)
Sowing date (day of year)
irrigated
rainfed
0
500
1000
1500
2000
2500
0 50 100 150 200 250 300 350 400
Irrigation (mm)
Sowing date (day of year)
Rainfall (mm)
Irrigation requirements and rainfall
0
10
20
30
40
50
60
70
80
150 160 170 180 190 200 210 220 230 240 250 260 270 280
0
200
400
600
800
1000
1200Irrigation (mm)
Irrigation sum = 1600 mmCumulative rainfall (mm)
Day of year
0
10
20
30
40
50
60
70
80
150 160 170 180 190 200 210 220 230 240 250 260 270 280
0
200
400
600
800
1000
1200Irrigation (mm)
Irrigation sum = 800 mm
Cumulative rainfall (mm)
Day of year
Hyderabad, India:Irrigation schedule
Percolation = 1 mm d-1
Percolation = 10 mm d-1